The optical communication technology is one of the fastest-growing technical fields at present, and the WDM technology is a preferred technology for implementing high-speed large-capacity data transmission in the optical communication network. With the development of the information industry and the growth of telecommunication services, the optical transmission network not only carries Internet services, but also is used as a bearer network for 3rd Generation Mobile Communications System (3G), Next Generation Network (NGN), Internet Protocol Television (IPTV), Virtual Private Network (VPN) and etc.
As a basis for carrying a variety of telecommunication services, the optical transmission network transmits a number of information, and once a fault occurs in a fiber channel of the optical transmission network or the optical transmission system fails, it is difficult to image how big the influence is and how serious the loss is, while on the other hand, in practical applications, it is difficult to avoid the fault in the network, and therefore, the protection for the optical transmission network is very necessary to the optical transmission network.
At present, most of the WDM systems belong to a double-fiber bidirectional ring network, which generally use protection modes of traditional 1+1 protection and 1:1 protection. In such two modes, each working path between every two nodes occupies one protection channel with a fixed wavelength. Therefore, it results in a number of wavelengths being occupied in the process of protection. While in areas where fiber resources are tight, it is general to use a single-fiber bidirectional ring network. If the protection modes of traditional 1+1 protection and 1:1 protection are used in the single-fiber bidirectional ring network, problems such as low resource availability etc. existing in the both protection modes will result in the fiber wavelength resources which are not abundant, becoming tighter.
As shown in FIG. 1, a diagram of a principle of using 1+1 protection and 1:1 protection in a single-fiber bidirectional ring network is illustrated, wherein, working paths are W1, W2, W3 and W4, and corresponding protection channels thereof are P1, P2, P3 and P4 respectively. As in the single-fiber bidirectional ring network, channels which are overlapped and intersected must use different wavelengths, the working paths W1 and W2 can use the same wavelength since they are neither overlapped nor intersected; however, as their protection paths are overlapped, W1 (W2), P1 and P2 at least need to occupy three different wavelengths; likewise, W3 (W4), P3 and P4 at least need to occupy three different wavelengths other than the wavelengths occupied by W1 (W2), P1 and P2. Thus, such mode needs to occupy many wavelength resources, especially when there are many services transmitted in the ring network, which will result in the wavelength resources being tighter.